Designing a modern 275..... - Page 8 - Ferrari Life
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post #141 of 316 Old 12-30-2011, 06:55 AM
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Originally Posted by mk e View Post
I agree it would be a whole lot easier to bond to square tubes, but you're still bonding and that is where all the uncertain comes into the game. Also for competition use you still basically scarp the frame after a hit or you go back and know out all the panels and re-do them.

You're point about using foam or honeycomb isn't really correct I don't think. You are absolutely right that adding fill will improve the bending strength (which is a function of thickness cubed) but I'm not sure that will help an awful lot in a shear load.....it will reduce any tenancy for the panel to buckle so you can count on it for compressive load not just tensile but there should be very little of either in a shear plate which should be in shear.

The 3rd dimension you are adding to the shear panels does give you the ability to make panels that are not flat if you chose so I think what you're envisioning is a monocoque design that you construct in a modular way with a steel safety cage buried inside. You and I are actually talking about very similar designs, your just uses more steel than I was thinking.
Yes, a 'semi-monocoque.' For repair you'd have to cut out the whole damaged panel and replace but once done it should be just as strong as before. Regarding shear panel strength, the sandwich prevents buckling but does not really improve shear, If you can load every panel in shear only it won't help much other than the fact that the attachment to the underlying frame will be twice as strong (which is the demonstrated weak point in the linked paper).

If you can get away with less steel, even better, but shear strength decreases over longer spans. Try twisting a tall boy vs a shortie. It's a delicate balancing act and I anticipate many hours of fea to try and optimize weight vs. necessary stiffness (10x max suspension stiffness is what I'm told is minimum, but I plan 5x that). To figure that out, I first need to determine how much aero downforce I can expect to generate and the resulting suspension stiffness needed and then I can think about how stiff the chassis needs to be while fitting it in that yet to be completed aero shape.

You're further along than I am since you have a body shape and dimensions, and you can probably use a round number like the 300lbs of downforce the 360 generates, add that to your expected fully loaded car weight with driver and come up with some wheel rates, track that back through the suspension to the pickup points and then figure out your necessary chassis stiffness.
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post #142 of 316 Old 12-30-2011, 09:57 AM Thread Starter
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Originally Posted by bobzdar View Post
Yes, a 'semi-monocoque.' For repair you'd have to cut out the whole damaged panel and replace but once done it should be just as strong as before. Regarding shear panel strength, the sandwich prevents buckling but does not really improve shear, If you can load every panel in shear only it won't help much other than the fact that the attachment to the underlying frame will be twice as strong (which is the demonstrated weak point in the linked paper).
This is where I'm still troubled. If you do a good job designing the frame then a torsional load will cause shear in ALL of the shear panels so although you can see a panel that was damaged in an impact and replace it, ALL the bond joints will be suspect I'd think?


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Originally Posted by bobzdar View Post
If you can get away with less steel, even better, but shear strength decreases over longer spans. Try twisting a tall boy vs a shortie. It's a delicate balancing act and I anticipate many hours of fea to try and optimize weight vs. necessary stiffness (10x max suspension stiffness is what I'm told is minimum, but I plan 5x that). To figure that out, I first need to determine how much aero downforce I can expect to generate and the resulting suspension stiffness needed and then I can think about how stiff the chassis needs to be while fitting it in that yet to be completed aero shape.

hmmmmm.....with a purely torsional load, the shear along the axis will be independent of length. There is long/short torsional stiffness difference difference that is directly proportional to the length but that is just because the shear is constant......so the longer you build the car the stronger you need to make the chassis to have equivalent displacements at the suspension points. That just makes sense.

In a really well done design the torsional stiffness will be directly proportional to weight telling you there are NO bending/moment loads (which are are geometry driven) driving the stiffness.
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post #143 of 316 Old 12-30-2011, 08:07 PM
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This is where I'm still troubled. If you do a good job designing the frame then a torsional load will cause shear in ALL of the shear panels so although you can see a panel that was damaged in an impact and replace it, ALL the bond joints will be suspect I'd think?





hmmmmm.....with a purely torsional load, the shear along the axis will be independent of length. There is long/short torsional stiffness difference difference that is directly proportional to the length but that is just because the shear is constant......so the longer you build the car the stronger you need to make the chassis to have equivalent displacements at the suspension points. That just makes sense.

In a really well done design the torsional stiffness will be directly proportional to weight telling you there are NO bending/moment loads (which are are geometry driven) driving the stiffness.
You'd have to test the chassis again after repair and see if the stiffness is the same, if not you've got problems but it would take a pretty big hit to kill the rest of the chassis in which case I don't know that I'd bother repairing it if even possible. I guess it would depend on the nature of the hit, similar to a steel spaceframe where if the hit was hard enough to tweak the rest of the frame, would you have confidence in it being repaired and straightened? The nature of the cf panels would either see them break or not, there would be no bending that could be missed as in a spaceframe. The key would be careful inspection of the bonding areas and I admittedly don't know enough about how the bonding agent behaves in that situation. If rivetted, you should be able to tell of the rivet area is damaged and could also measure for trueness as you know if the underlying steel frame is out of whack, your panels are no longer secure.

Regarding shear strength over a long distance, it's the resistance to buckling that decreases as the length increases. The sandwich construction prevents buckling and the steel frame members can reduce the span allowing you to use a thinner CF skin. For me it's more ease of manufacture than trying to do a true mono, it should be significantly lighter than a space frame and easier to make than a mono while also allowing easier rule passage. You don't have that concern, but your tub will be even bigger.

If you think you can do a full mono, I say go for it. Tornado makes a full CF monocoque gt40 tub and I don't think they are a huge operation, so it's doable. I know it weighs a lot less than their spaceframe or aluminum mono chassis, but don't know a whole lot about relative strength. It's the only instance I'm aware of where you can directly compare the same design in a spaceframe to aluminum or CF monocoque, I just haven't found any stiffness results.
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post #144 of 316 Old 01-05-2012, 01:02 PM
 
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Another reason I like shear panels is simply that they are easy means to keep out the breeze.

Think of all the places that need to be blinded off from the outside.

For example, floor pans and bulkheads.

By laminating up a few layers(this panel can be contoured) you can incorporate/integrate comb inside, or foam strips.
These strips can be say 75mm wide, 6-12mm thick, in turn these form ribs, or members inside the panels making them extremely strong in bending forces, from something like a seat, or dash mounting point etc.

Within these foam or core ribs, you can add hard points for threaded inserts.

By using these CF shear panels, they allow you to do away with diag tube members, and all the other stuff you need to add in there in order to bolt a seat to.
I cant believe you can provide a mounting point, a diag brace, and a form of closing off the section, all in steel, or alloy, lighter than you can with CF panels.
Since the tooling budget needed for stamping, or hot hammering steel or AL alloy sheet into is insane, think milled steel tools, CF panels also excel here too.
All you need is a primed mdf tool, or cast epoxy to form CF panels of any shape.

If you steer away from hard tooling for forming steel panels, then your limited to panels fabricated in a more modular way either with welding, bonding, or riveting. This has drawbacks, weight, and limited to more angular forms(stress risers) being the main two that spring to mind.

For more info on CF forms with hard points, and details of fabricating CF items featuring hardpoints for inserts look at the links below.
They feature some r+d I did on two F1 CF constructions to get a little more insight in their construction.
Rear crash structure,

Rear crash structure, a closer look. - Forum - F1technical.net

CF pushrod, with Ti bonded insert,

Carbon Fibre pushrod, a closer look. - Forum - F1technical.net

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post #145 of 316 Old 01-05-2012, 11:00 PM
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Exterior Design Revealed

It's been a long time coming and Mark has been extremely patient as I have worked to finalize the exterior theme for the car. Going into the project, one has to remember that doing anything regarding a 275 other than restoring it, is tantamount to a suicide mission. This is a suicide mission of the highest order. Knowing that....

Our goal was not to remake the 275, but to imagine for ourselves, what the theme would be for a front engine, V12 powered, compact, lightweight super coupe if it were made today. Personally, the 275 is one of my all time favorite designs. I got to baby sit one once for 3 days when I was college. The experience was something I kept with me throughout my automobile design career and even to this day. Mark, Dave and I continuously use words like "elegant", "powerful", "adult", "beautiful", "something you'd love to wax" etc., when talking about what we want this car to be. So while I know this is a suicide mission, I think I have come up with something that is classic, tasteful and yet moves the needle forward in coupe design.

The "problem" with older designs is that, for the most part, the body sides tend to be very one dimensional in the plan view. They are pretty flat. One way to bring our car into the 21st century is to add a whole boat load of positive plan view sweep in the body side and then "pull" the wheel openings out to meet the tires. This is going to yield an extremely three dimensional design that will have the light and reflections dancing all over it. Classic in proportion, yet modern in it's surface treatment.

Every front engine/ rear drive coupe has the "kick up" ahead of the rear wheel. My theme acknowledges this design element but does it in a new way. Instead of the kick up, a nose to tail arcing line moves through the rear fender and I alter the sail panel surface above it to create an abstraction of the kick up. Again, simple, elegant, classic and new at the same time.

For the front end, originally we discussed the using an off the shelf round lamp, and finally settled on the lamp from the current production California. It did everything we needed it to do, gave the expression I was looking for and integrated into the fenders and nose sections that were already established. The various sketches show the development.
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post #146 of 316 Old 01-06-2012, 04:25 AM Thread Starter
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Thanks for posting Mike! Now I need to get some of the other projects off my plate so I can start building this

It's almost time to start handing stuff to Dave who will be doing the CAD work. I'm guessing the CAd phase will take another 6 - 12 months to complete with Dave doing the modeling, Mike specing/reviewing the shape of stuff that shows and me specing/reviewing the the stuff that doesn't show but it expected to function.

This is a big project even by my twisted standards
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post #147 of 316 Old 01-06-2012, 06:18 AM
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Mike & Mark, it looks super. Love the front, and how you've managed to give it its own graceful, sloping look without any Porsche DNA. Having the hood scoop and the California headlights really help. The sail looks terrific too, but I'll bet there's going to be a nasty blind spot there. Still wouldn't change it though..... It's gorgeous as is. The only thing I'd probably change if it were me, is the chin spoiler. In the last sketch it looks similar to the 550's winglets, and I'd probably make it a little less aggressive and more like the 575's. It would also make it less prone to getting damaged or ripped off (known problems with the 550's winglets).

Is the bottom rendition pretty much it, then? Love that ghosted 275 in the background.

Any particular reason why the new version has 3 gills per side in lieu of the original's 4? That wouldn't be a subtle little signature feature from the 3 guys who are working on this perhaps?

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post #148 of 316 Old 01-06-2012, 12:06 PM
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Very cool. It looks somewhat like the Fiskar (sp?) - which is a very elegant design in its own right.
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post #149 of 316 Old 01-06-2012, 12:15 PM
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Mike- Very pretty design. Look forward to this project.

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post #150 of 316 Old 01-06-2012, 12:28 PM
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The topmost of the renderings is undoubtedly what does it for me. The headlamp treatment and grill opening is very nice. The rest is also quite wonderful looking. The front end is not entirely unlike the Maserati GS Zagato only the Maserati appears to have somewhat softer lines. The above is a somewhat harder look in comparison which is definitely what I prefer.
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post #151 of 316 Old 01-06-2012, 07:38 PM
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This is beyond cool. The third drawing in particular is the bee's knees.
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post #152 of 316 Old 01-06-2012, 11:47 PM
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Drawings look superb. I think you captured the essence of the 275 GTB very well and did not loose it in the "modernization",
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post #153 of 316 Old 01-07-2012, 02:58 AM
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Mike- Very pretty design. Look forward to this project.
I concur.


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post #154 of 316 Old 01-07-2012, 03:51 AM Thread Starter
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This is beyond cool. The third drawing in particular is the bee's knees.
It'll be a lot of work but rumor has it you'll be in need of a new project soon and you don't live that far away
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post #155 of 316 Old 01-07-2012, 06:50 AM
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I think you hit the design out of the park...Only concern is will a 456up v12 fit under that hood? If I understand the dimensions right, it's going to be a 355 sized car. How about your frankenrossa v12?
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post #156 of 316 Old 01-07-2012, 07:54 AM
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It'll be a lot of work but rumor has it you'll be in need of a new project soon and you don't live that far away
I did get a little bored while on vacation last week without having any 308 time... If I didn't know better, I'd almost think that I like doing these projects.
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post #157 of 316 Old 01-07-2012, 08:06 AM
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The drawings looks magnificent guys. Can't wait to see this become a reality!

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post #158 of 316 Old 01-07-2012, 09:23 AM Thread Starter
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...Only concern is will a 456up v12 fit under that hood? If I understand the dimensions right, it's going to be a 355 sized car. How about your frankenrossa v12?
I THINK a 456/550/575/599/612 V12 will fit. This is the kind of stuff that gets fully sorted in the next phase though and there will likely be some give and take here and there.

Mike is finishing up the concept sketches then Dave will transfer them into a 3D modeling package.

Next Dave will add the main mechanical components. We'll work together to get them where they need to be and fit.....if this can't be accomplished we go back to Mike begging for more room
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post #159 of 316 Old 01-07-2012, 01:38 PM
 
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I THINK a 456/550/575/599/612 V12 will fit. This is the kind of stuff that gets fully sorted in the next phase though and there will likely be some give and take here and there.

Mike is finishing up the concept sketches then Dave will transfer them into a 3D modeling package.

Next Dave will add the main mechanical components. We'll work together to get them where they need to be and fit.....if this can't be accomplished we go back to Mike begging for more room
Throw in a torque tube while your at it

Love the lines, its perfect, well done Mike.

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post #160 of 316 Old 01-07-2012, 10:19 PM
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Mike & Mark, it looks super. Love the front, and how you've managed to give it its own graceful, sloping look without any Porsche DNA. Having the hood scoop and the California headlights really help. The sail looks terrific too, but I'll bet there's going to be a nasty blind spot there. Still wouldn't change it though..... It's gorgeous as is. The only thing I'd probably change if it were me, is the chin spoiler. In the last sketch it looks similar to the 550's winglets, and I'd probably make it a little less aggressive and more like the 575's. It would also make it less prone to getting damaged or ripped off (known problems with the 550's winglets).

Is the bottom rendition pretty much it, then? Love that ghosted 275 in the background.

Any particular reason why the new version has 3 gills per side in lieu of the original's 4? That wouldn't be a subtle little signature feature from the 3 guys who are working on this perhaps?
Thank you for the kind words.

The splitter that wraps around the car is the easiest thing to change. The team spoke about have some form of modern aero management. That is the idea that is reflected in the splitter and diffuser. What form they ultimately take will be decided later in the process.

Yes the bottom sketch is the car as it shows all three elements of any car design, proportion, surface development and details.

How astute of you to notice.
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